Trump doesn't need to make a deal with Republicans to get them to block Ukraine aid. Republicans see Putin as a fellow conservative, they care more about THAT than democracy or law or US Interests, and they've been building connections with him since before the George W. Bush presidency.
People forget it, or just weren't aware enough of politics at the time to know it, but GWB was weirdly friendly to Putin during his presidency, and this coincided with evangelicals starting to effusively praise Putin as a "godly" leader(mostly and explicitly because of his persecution of queer people, but also cuz he's a tyrant and conservatives love tyrants), and generally talking up his regime, and with Republican pols doing all sorts of skeezy deals with him in Eastern Europe, helping him to prop up pro-Kremlin dictators. At the same time the GWB administration did little(or nothing, honestly, that I ever read about) at all to push back against Putin's campaign to build violent, often fascist, separatist client-movements in the post-soviet countries, culminating of course in GWB 1)promising Georgia the US would support their sovereignty then 2) standing by doing nothing during Putin's brutal invasion of Georgia in support of the violent separatist clients he was funding in THAT country. This would continue throughout the Obama years as Republicans pitched Putin to themselves as Obama's geopolitical "rival"; talking him up to truly absurd degrees especially online.
tl;dr: The Republican Party was already in bed with Putin by, at least, 2008, and didn't need any convincing from Trump. Remember that JEFF SESSIONS(look at this dude's history with the party) was an early supporter of his campaign and PERSONALLY INVOLVED in all the Russia shit his campaign did. Remember that Mitch McConnell Refused to Join Obama in condemning Russian espionage interfering with the 2016 election. The Republican Party, to its highest levels, sees Putin as its ally, and democracy as the biggest obstacle to their rule.
