Even after Jeb Bush was caught off guard by a comeback from Florida Sen. Marco Rubio in last week's debate, Bush has vowed to keep up the attacks on Rubio's attendance record in the Senate.

Hillary Rodham Clinton and Ben Carson are tied in a hypothetical head-to-head matchup in a new poll released Tuesday, a year out from when voters are set to cast ballots in the 2016 general election.

Though Clinton is tied with Carson at 47%, the former secretary of State leads three other major Republican candidates, according to the NBC/News Wall Street Journal poll.

In recent weeks, Carson, a retired neurosurgeon, has shot to the top of the crowded GOP presidential field, appealing to an electorate seeking a political outsider.

When Clinton, the Democratic front-runner, is pitted against Florida Sen. Marco Rubio, she leads him 47% to 44%. Moreover, when matched up against former Florida Gov. Jeb Bush and billionaire businessman Donald Trump, she leads 47% to 43% and 50% to 42%, respectively.

But Clinton has a clear weakness in the poll and it’s with independent voters, who are throwing most of their support behind GOP candidates. Many swing states, such as Colorado, have large blocs of independent voters that can tilt elections.

Among independent voters, Carson leads Clinton by 13 percentage points, while Rubio outpaces her by 7 percentage points.

The poll was conducted Oct. 25-29 and surveyed 847 registered voters. It has a margin of error of plus or minus 3.4 percentage points.

As Republican presidential hopefuls voice concerns about future debate formats, New Jersey Gov. Chris Christie offered some pointed remarks on CNN.

Donald Trump called on lower-polling fellow Republicans to drop out of the presidential race Tuesday, peppering his rivals for the nomination with unsolicited advice and criticisms.

“If a person has been campaigning for three or four months and they’re at zero, 1% or 2%, they should get out,” he said, without naming names.

At a news conference in New York to promote his latest book, Trump also attacked Ben Carson, who has overtaken him as the front-runner in a series of polls, for wanting to get rid of Medicare. Trump criticized the physician for having “low energy,” a favorite insult of his.

Trump also labeled Sen. Marco Rubio of Florida as “weak on immigration” and criticized Rubio’s “bad record of finances” and missed Senate votes.

The promotional stop for Trump’s book, “Crippled America: How to Make America Great Again,” at Trump Tower on Fifth Avenue, essentially doubled as a campaign event as Trump finds himself fighting to regain the lead in the GOP primary.

"I am telling it like it is and going to the heart of what I think will make America great again,” Trump wrote in the book, whose intended audience is made up of the same voters who helped propel him to the top of the Republican field this summer.

More recently, though, Trump's status as the undisputed front-runner has faltered. A new NBC News/Wall Street Journal poll shows Trump with 23% of the support of likely Republican primary voters, trailing Carson, who leads with 29%. The findings were similar to a New York Times/CBS poll last week.

NBC’s poll was conducted both before and after last Wednesday’s raucous Republican presidential debate hosted by CNBC. Trump accused the media of being tough on Republicans and soft on Democratic front-runner Hillary Rodham Clinton in debates.

Trump rocketed to the top of the polls over the summer in part because of controversial comments about Latinos and illegal immigration. In his book, Trump blames President Carter for opening the country's borders to "anyone who came here” and the Mexican government for advocating illegal border crossings in how-to pamphlets. A 1,000-mile wall, he wrote, should be built to secure the border.

On Tuesday, Trump said he would make Mexico pay for construction of the wall because the country owes billions of dollars to the U.S.

The former reality-TV star also took shots at one of his favorite targets: the media, which he acknowledged he tries to use to his advantage. “Sometimes I make outrageous comments and give them what they want – viewers and readers – in order to make a point,” he wrote.

He appeared early Tuesday to be getting what he wants: His book was already listed in the top 200 in sales on Amazon.com.

Trump promised to donate his profits from the 208-page book to veterans’ groups and others.

The 11 hours Hillary Rodham Clinton spent at the House Benghazi committee last month appears to have been time well spent: The former secretary of State has significantly improved her standing among key groups of voters, a new poll indicates.

Among Democratic primary voters, 72% said they were now satisfied with Clinton's responses to questions about how she handled the attack on the U.S. diplomatic compound in Benghazi, Libya, in 2012, according to the Wall Street Journal/NBC poll. That's up from 58% before her testimony.

Clinton made progress as well among swing voters, the survey found. Before her testimony, 84% of swing voters had said they were not satisfied with her responses to questions about Benghazi. In the latest survey, only 40% said so.

That does not mean Clinton has completely persuaded swing voters; only about 1 in 4 said they were satisfied with her answers. But it does suggest that the testimony has gone a long way toward neutralizing the issue among voters who have not already made up their minds to oppose her.

Gun control tops Hillary Rodham Clinton’s agenda as she heads to Iowa to campaign on Tuesday. Clinton, the Democratic presidential front-runner, kicked off her trip with a new TV ad focused on gun violence and gun control. The 30-second spot shows Clinton talking with the members of the public at a New Hampshire town hall meeting just after the mass shooting at a community college in Roseburg, Ore., last month.

“We’re better than this. We need to close the loopholes and support universal background checks,” Clinton said in the video. “How many people need to die before we actually act?"

The ad debut comes a day after Clinton met with the mothers of Michael Brown, Trayvon Martin and Tamir Rice, three young black men who died in shootings between 2012 and 2014, two killed by police. Clinton and rival Bernie Sanders also have met separately with leaders of the Black Lives Matter movement to discuss what changes the group wants to see in how the federal government addresses gun laws.

Clinton's efforts to call out the National Rifle Assn. over gun control is an indication of her shift to the left since her 2008 campaign, particularly as she faces a challenge from the more liberal Sanders.

Take a look at Clinton’s TV ad:

When her fans sold Elizabeth Warren baby onesies and donned “Warren for President” hats this year and last, the Massachusetts senator insisted that she would not run for the White House. But with those demurrals came a promise to use her clout to push Democrats to the left as the de facto leader of her party’s populist wing.

Five months after her most zealous backers officially moved on to other candidates, the Democratic Party’s issues in 2016 are largely Warren’s issues: college affordability, Wall Street accountability, Social Security without compromise, skepticism about a Pacific trade deal.

“The goal we’ve had all year is to make sure that 2016 is fought over Warren-wing ideas,” said Adam Green, co-founder of the Progressive Change Campaign Committee, a group that has tried to align itself with her brand. “And that’s absolutely come true.”

Even Warren’s allies concede that she can’t take full credit for the party’s shift. Rising anger at institutional elites and the emergence of Sen. Bernie Sanders, whose focus on a financial system “rigged” for the wealthy overlaps with Warren’s rhetoric, have played major roles in pushing the Democratic campaign debate and the party’s front-runner, former Secretary of State Hillary Rodham Clinton, leftward.

Yet, Warren has clearly had a major impact. The question now is whether she can maintain her cudgel as Clinton solidifies her strength and the party appears to be coalescing around her.