The president is looking to buck up senators coming under mounting pressure on impeachment. Gardner, who is widely seen as the most jeopardized Republican incumbent up for reelection, faced criticism earlier this month after he dodged questions about Trump’s conduct. Ernst was confronted at a town hall over her support for the president. This week, a liberal group began a multimillion-dollar advertising campaign pushing both Republican senators to support impeachment.

The new online fundraising drive bypassed Collins, an occasional Trump critic who called on the president to retract his tweet comparing the impeachment investigation to a “lynching.” Collins also said Trump made a “ big mistake” in asking China to investigate the Biden family.

Arizona Sen. Martha McSally, another vulnerable Republican facing reelection, was also omitted, though apparently for a different reason. While McSally signed onto the anti-impeachment resolution, she has frustrated Republican officials over her reluctance to exclusively use WinRed, a Trump-endorsed online fundraising tool. Party officials are trying to turn WinRed into a centralized hub of small-donor giving ahead of the 2020 election and used the platform to send out Trump’s appeal for the three senators.