Republicans' growing unity behind Donald Trump has helped pull him just 1 percentage point below Hillary Clinton and placed GOP leaders who resist him in a vulnerable position, according to the latest Washington Post-ABC News Tracking Poll.

A majority of all likely voters say they are unmoved by the FBI's announcement Friday that it may review additional emails from Clinton's time as secretary of state. A little more than 6 in 10 voters say the news will make no difference in their vote, while just over 3 in 10 say it makes them less likely to support her; 2 percent say they're more likely to back her as a result.

The issue may do more to reinforce preferences of voters opposed to Clinton than swing undecided voters — roughly two-thirds of those who say the issue makes them less likely to support Clinton are Republicans or Republican-leaning independents (68 percent), while 17 percent lean Democratic and 9 percent are independents who lean toward neither party.

When asked about House Speaker Paul Ryan's decision not to campaign for Trump in the final weeks, two-thirds of Republican-leaning likely voters disapprove of the move (66 percent), including nearly half who disapprove "strongly" (48 percent). Barely 1 in 5 approve of Ryan's decision, 21 percent.

The Post-ABC Tracking Poll continues to find a very tight race, with Clinton at 46 percent and Trump at 45 percent among likely voters in interviews from Tuesday through Friday, followed by Libertarian Gary Johnson at 4 percent and the Green Party's Jill Stein at 2 percent. The result is similar to a 47-45 margin in the previous wave released Saturday, though smaller than found in other surveys this week. When likely voters are asked to choose between Clinton and Trump alone, Clinton stands at 49 percent to Trump's 46 percent, a margin that is still statistically insignificant.

Greater Republican unity has buoyed Trump's rising support, which has wavered throughout the year. Trump's 87 percent support among self-identified Republicans, ticking up from 83 percent last week nearly match Clinton's 88 percent support among Democrats. Independents also have moved sharply in Trump's direction, from favoring Clinton by 8 points one week ago to backing Trump by 19 points.

Clinton is still widely seen as more qualified for the presidency, leading the measure by an 18-point margin, 54 to 36 percent. She has held a clear advantage over Trump in qualifications throughout the campaign.

But Trump receives more unified backing among those who see him as better qualified. Fully 99 percent of this group currently supports him, compared with Clinton's 84 percent support among those who see her as better qualified. Another 7 percent of this group supports Trump, while 4 percent are for Johnson and 2 percent for Stein.

Clinton's also lost a once-large advantage on empathy, where voters now split 46 percent for her and 43 percent for Trump when asked which candidate understands the problems of people like them. Clinton had led Trump by an 8-point margin on this measure in early September among likely voters and by a 20-point margin among all adults in August.

Clinton has a narrow 8-point edge over Trump on which candidate has stronger moral character, 46 to 38 percent. A sizable 13 percent volunteer that neither candidate possesses this trait. A larger share of Trump supporters than Clinton supporters say neither candidate has strong moral character (12 percent vs. 2 percent).

House Speaker Paul Ryan's decision not to campaign for Trump this fall has proven unpopular among his fellow partisans. This as Ryan's status as speaker is in peril through Republican infighting.

Rejection of Ryan's stance swells to 75 percent among Republicans and GOP-leaning independents who identify as "very conservative" compared with smaller majorities of "somewhat conservative" Republicans (63 percent) and those who are moderate or liberal (56 percent).

Ryan's stance against Trump is being handled differently by several other prominent Republicans. Jason Chaffetz, R-Utah, has said that even though he could not endorse Trump nor his actions, he still plans to vote for the Republican nominee.

Maryland Gov. Larry Hogan, a popular Republican governor in a overwhelmingly Democratic state, has spoken out against Trump, a move that was widely popular with independents and Democrats in the state, but Republicans were split on whether they approved of the decision.