With the election just one week away, Republican Marsha Blackburn is now leading Democrat Phil Bredesen in Tennessee's U.S. Senate race by at least 5 percentage points in two new polls released Tuesday.

Her lead comes after a pair of polls earlier this month had showed a closer dead heat.

A new NBC/Marist poll has Blackburn, a congressman from Williamson County, with support from 51 percent of likely voters, compared with 46 percent for Bredesen, a former Tennessee governor.

The poll, taken between Oct. 23 and Oct. 27, was a sample of 471 likely voters with a margin of error of 5.7 percentage points.

ELECTION 2018: Full coverage of Tennessee races

A separate poll from Vox Populi Polling has Blackburn up by 7 points, 48 percent to 41 percent, when isolating voters who say they've made up their minds on who they back.

The poll found Blackburn has a 6-point lead, 53 percent to 47 percent, when factoring in how undecided voters are leaning. The online poll of 780 active voters was taken between Oct. 27 and Oct. 29 and has a margin of error of 3.5 percentage points.

Blackburn's lead coincides with soaring popularity for President Donald Trump, who now has support of 56 percent of likely voters in the NBC/Marist poll, compared with 39 percent who don't support his job performance. That's compared with 47 percent who approved of the president and 43 percent who disagreed with him two months ago.

'A dose of reality'?

The latest polls come as Blackburn has for weeks sought to capitalize on the partisan-driven fight over the confirmation of Supreme Court Justice Brett Kavanaugh and a caravan of thousands of migrants making their way through Central America and Mexico.

A previous NBC/Marist poll taken in August had Bredesen up 2 percentage points. A prior Vox Populi poll conducted in September also had Bredesen leading by 2 percentage points.

More recent polls, from Reuters and Vanderbilt University, in mid-October had Blackburn up 3 percentage points and Bredesen up 1 percentage point, respectively. That was after Blackburn was shown leading by 14 percentage points and 8 percentage points in New York Times and CBS polls, respectively, at the beginning of the month.

"The shift in Blackburn's favor may be a dose of political reality for Bredesen in Tennessee, where President Donald Trump won by 26 points in 2016," states an NBC/Marist analysis of the poll results. "The poll's sample shows that 43 percent of likely voters identify as Republicans, while just 27 percent identify as Democrats."

Bredesen's favorability numbers dip after barrage of ads

In both polls, Bredesen has seen his net favorability marks decrease from what they were two months ago after a barrage of negative ads waged by Blackburn and outside conservative groups.

Fifty-two percent of respondents in the NBC poll said they view Bredesen favorably compared with 39 percent who do not. That's a 13-point difference between favorable and unfavorable marks, down from a 39-point spread in the previous poll.

But in the Vox Populi poll, Blackburn now has higher favorability than Bredesen, 45 percent to 41 percent.

"In the weeks leading up to Election Day, Congresswoman Marsha Blackburn has rallied Republican voters to help solidify her base," said Macy Cambio, Vox Populi Polling managing director.

"With Phil Bredesen's image now underwater and Blackburn opening up a seven-point lead, the chance of this seat flipping Democratic looks much slimmer than it did just one month ago."

Vox Populi Polling, based in Virginia, was founded in 2014 by a group of Washington Republicans that included Mary Cheney, a political strategist and daughter of former Vice President Dick Cheney, according to Politico.

Blackburn gets bounce as Bredesen takes hit from Republicans

Perhaps concerning for Bredesen is the hit he's taken from Republicans, who helped him win two terms as governor and whom he has courted to compete in a politically red state.

The NBC poll found that 39 percent of Republicans gave Bredesen favorable reviews in August, but that's down to 24 percent in the latest survey.

Blackburn has sought aggressively to tie Bredesen to the national Democratic politics of Senate Minority Leader Chuck Schumer, D-N.Y., to push back at his centrist, independent-minded reputation as a governor.

In addition to the uptick in Trump's popularity, 54 percent of Tennessee voters now indicated a preference for Republicans to win Congress, up from 50 percent in August.

Bredesen took heat from some in his own party for supporting Kavanaugh's nomination. But the NBC poll found that it has resulted in no backlash in the polls. He now enjoys a plus 86 percent positive rating from Democrats, up from a plus 83 percent positive rating two months ago.

Lee maintains double-digit lead in governor's race, both polls say

The poll found Kavanaugh's confirmation was popular in Tennessee despite the allegations of sexual assault he faced.

Forty-two percent of respondents in the NBC/Marist poll said they are more likely to back a candidate who supported his confirmation, while 27 percent say they are more likely to back a candidate who opposed Kavanaugh''s nomination.

In the race to replace term-limited Gov. Bill Haslam, Republican Bill Lee maintains a sizable lead over Democrat Karl Dean, according to both polls.

In the NBC/Marist poll, Lee, a businessman from Williamson County, is ahead 57 percent to 40 percent over Dean, former Nashville mayor.

According to Vox Populi Polling, Lee is supported by 56 percent of likely voters compared with 44 percent for Dean.

Lee has led in every public poll released since the August primary.

Reach Joey Garrison at jgarrison@tennessean.com or 615-259-8236 and on Twitter @joeygarrison.