This story was updated Feb. 20, 2018, at 11:45 p.m.

NASHVILLE — Americans for Prosperity, a group funded by the conservative billionaire Koch brothers, and another political action committee that supports President Trump say they are solidly committed financially to Republican U.S. Senate hopeful Marsha Blackburn's candidacy.

And that's regardless of whether incumbent U.S. Sen. Bob Corker, R-Tenn., reverses his decision not to run and jumps into the contest.

In a statement last week, AFP President Tim Phillips pointed to U.S. Rep. Blackburn's support in efforts to repeal the Affordable Care Act and her backing of tax cuts, calling her "a tireless advocate for taking on the injustices of top-down, failed, big-government policies" and adding, "she has AFP's strong support."

AFP-Tennessee Director Tori Venable, meanwhile, said Tuesday that extends to the state group, which she noted will include "express advocacy" for the first time in a Tennessee political campaign. The Tennessee group has previously run political issue ads saying a candidate has or hasn't backed a particular issue, but has stopped short of actual endorsements.

Meanwhile, the Committee to Defend the President—America, a super PAC, says it will spend $1 million in support of Blackburn — and attacking Corker — if the former Chattanooga mayor decides to get in.

Corker's staff said last week the senator is "listening closely" to those they say are encouraging Corker to get in the race after former Republican U.S. Rep. Stephen Fincher announced last week he was dropping his U.S. Senate primary bid.

Fincher said he hoped Corker would get in.

Some Tennessee Republicans have been nervous whether Blackburn, an outspoken conservative, can beat Democrat and former Tennessee Gov. Phil Bredesen in the general election. A poll commissioned by a business group found that Bredesen led Blackburn in the general election by 2 percentage points.

But if Corker decides to run for re-election, the Committee to Defend the President is pledging to spend $1 million in the primary to defend Blackburn's record and "expose" what it calls "Sen. Corker's anti-Trump agenda."

"Whether establishment darling Bob Corker decides to run or not, Marsha Blackburn is poised to become Tennessee's next Senator—and defend the Trump agenda in the Senate," said the group's spokeswoman, Amanda Head, in a news release.

She added: "We're coming for you, Bob."

The Committee to Defend the President also released what it said is a survey of 400 likely Tennessee GOP primary voters. Conducted Feb. 13-15 by WPA Intelligence, it says Blackburn had a nearly 2-1 edge, or 40 percent to 22 percent, over Corker. That had about a 4 percent margin of error.

A wider sampling of 500 voters, including Democrats, found Blackburn led former Tennessee Democratic Gov. Phil Bredesen by 44 percent to 35 percent, with a 4.4 percent margin of error, according to the poll.

Contact staff writer Andy Sher at or 615-255-0550. Follow on Twitter @AndySher1.