Ed O'Keefe contributed to this report.

Albuquerque, N.M. - Top Republican Party leaders on Wednesday began sensitive discussions over the scope of support the GOP can give now to President Trump's re-election campaign, amid talk of potential primary challenges, fresh evidence of sagging approval ratings and multiple ongoing government investigations.

Members of a Republican National Committee (RNC) panel responsible for considering formal resolutions and changes to party rules on Wednesday affirmed their support for the president by passing a resolution offered by Oklahoma Committeewoman Carolyn McClarty that stated the party's "unequivocal support" of the president — a step that a president's own party has never before taken.

Get updates from the campaign trail delivered to your inbox

But the ongoing special counsel investigation and intra-party squabbles could threaten Mr. Trump's standing as the presumptive nominee. Maryland Governor Larry Hogan, former Senators Bob Corker and Jeff Flake, Utah Sen. Mitt Romney, and former Ohio Governor John Kasich have all been mentioned as potential challengers to Trump for the 2020 GOP presidential nomination — although none of the men have taken formal steps to begin a campaign.

All 168 members of the RNC will vote on the resolution during its general session here on Friday.

The resolution follows a commitment the RNC is already making to share its data, polling, and infrastructure with the Trump-Pence reelection campaign. But members of the RNC resolutions committee decided not to consider another potential resolution that would express support "for the re-nomination" of Trump and Vice President Pence.

Jevon Williams, an RNC member from the Virgin Islands, said in an email obtained by CBS News that he had submitted the resolution explicitly supporting re-nomination because "words matter," and the party should have no doubts about working for Mr. Trump's reelection. But his resolution did not receive a motion in the committee and was never voted on.

No resolution passed during the annual RNC winter meeting will change the rules of the 2020 GOP primary and nomination process, because those rules were finalized in 2016. Also, it's the state parties that mostly set the rules of how they hold their primaries. For example, the New Hampshire GOP had been considering changing its primary rules to prevent a challenger, but a proposed change ultimately wasn't formally submitted for consideration by the deadline.

On the sidelines of the RNC winter meeting in Albuquerque, members are also performing an autopsy of the 2018 midterm elections with state executive political directors, digital firms, and lobbying groups that are already thinking about the 2020 battle for Congress.

Republicans are already closely monitoring developments in upcoming Senate races in Georgia, Kentucky and Tennessee. Sen. David Perdue, of Georgia, who is a close Trump ally, could face a challenge from Democrat Stacey Abrams, who narrowly lost a bid for governor while amassing a national political network. National Republicans are trying to convince Secretary of State Mike Pompeo, a former Kansas congressman, to run for the seat of retiring Sen. Pat Roberts, R-Ky., partly in hopes of keeping former Kansas Secretary of State Kris Kobach — an outspoken proponent of strict immigration controls who upended the state's gubernatorial race last year — from seeking the seat. And in Tennessee, Republicans are still sorting out who might run to succeed retiring Sen. Lamar Alexander.

Editor's note: An earlier version of this report said that Kris Kobach was Kentucky secretary of state, rather than Kansas secretary of state. The story has been updated.