The deeper Donald Trump's Russia scandal goes, the more fissures we are starting to see within the GOP. Two House Republicans signed on to a letter Friday penned by Democrats asking the congressional committees with oversight over the IRS to seek copies of Donald Trump's tax returns. Cristina Marcos writes:

Reps. Mark Sanford (R-S.C.) and Walter Jones (R-N.C.) signed a letter urging the chairmen of the House Ways and Means Committee and Senate Finance Committee to ask for copies of Trump's tax documents from the last decade.

The letter was spearheaded by Rep. Bill Pascrell (D-N.J.) and signed by most of the 193-member House Democratic Caucus. It argues that letting members of Congress see what’s in Trump’s tax returns would clear up any questions about whether his business ties offer conflicts of interest. [...]

“Disclosure would serve the public interest of clarifying President Trump's conflicts of interest in office, the potential for him to personally benefit from tax reform, and ensure that he is not receiving any preferential treatment from the IRS,” the letter states.

For four decades, American presidential nominees have gone through the ritual of releasing their tax returns in the interest of demonstrating their ability to serve voters first and foremost. But Trump, with business interests spanning the globe, has insisted on keeping his returns away from public scrutiny.

The move by Sanford and Jones is part of a slow evolution for both men. Earlier this week, they both voted "present" on a failed measure requesting committee access to a decade of Trump's returns.

While we're still not seeing any profiles in courage from congressional Republicans, their fidelity to Trump is starting to waver. On Thursday, both House and Senate Republicans increasingly joined the call for Attorney General Jeff Sessions to recuse himself from FBI investigations into the Trump campaign's contacts with Russia.

The longer the Russia scandal brews, the more squeamish Republicans on the Hill will get. Watch for it.