Washington (CNN) The Democratic candidate in a tight House race in Pennsylvania says in a new ad that linking him to House Minority Leader Nancy Pelosi is "a big lie."
Two weeks before the special election to replace former Rep. Tim Murphy in deep-red western Pennsylvania's 18th District, Conor Lamb launched a TV ad responding to Republican state Rep. Rick Saccone's efforts -- backed by millions in pro-Saccone outside spending -- to tie him to the California Democrat.
"My opponent wants you to believe that the biggest issue in this campaign is Nancy Pelosi. It's all a big lie," Lamb said in the ad. "I've already said on the front page of the newspaper that I don't support Nancy Pelosi. The real issues are the ones that affect your lives."
Trump's unpopularity has put a vast swath of typically safe Republican-held congressional seats in jeopardy in November's midterm elections. A new CNN poll conducted by SSRS found that 54% of registered voters say they back a Democrat in their congressional district, while just 38% prefer a Republican.
The March 13 Pennsylvania special election is something of a test case, because the district voted for Trump over Hillary Clinton by 20 percentage points in 2016, and backed Mitt Romney by 17 points in 2012. There are more than 100 GOP-held House seats where Republicans have less of an advantage by that measurement -- and if Lamb wins, it would signal that many more of those seats are vulnerable.
Pelosi is deeply unpopular among Republican voters. The party hopes to drive moderates and GOP-leaning independents back into its arms by shifting key races' focus from Trump to Pelosi.
The argument: Lamb would nudge Democrats closer to the 24 seats they need to flip in order to take control of the House -- and if that happens this fall, Pelosi would become speaker.
That Lamb needed to respond to those GOP ads is an indication they've been effective. His response could offer a template for other Democrats to use this fall, in midterm elections where some within the party have feared Pelosi could be an anchor around Democratic candidates.
A Monmouth University poll showed Lamb is within striking distance, trailing Saccone 49% to 46%.
That's why Republicans have pulled out all the stops. Trump and Vice President Mike Pence have visited the district. House Republicans' campaign arm and a House Speaker Paul Ryan-aligned super PAC have spent millions on the race; a pro-Trump super PAC said last week it will spend $1 million.
The GOP spending has overwhelmingly gone to air television advertisements that link Lamb to Pelosi -- even though he said at the outset of the race that he didn't support Pelosi for House speaker.
National Democrats, aware that the party's brand is unpopular in western Pennsylvania and that Lamb has outraised Saccone, have largely stayed out of the race.
"We'll continue to monitor that election day by day. But make no mistake: Conor will have the resources he needs to compete," New Mexico Rep. Ben Ray Luján, the Democratic Congressional Campaign Committee chairman, told reporters earlier this month.
The Democratic group Ending Citizens United is spending $250,000 on ads criticizing Saccone's record as a state lawmaker.