Swing-state Democratic incumbents, like Senators Raphael Warnock of Georgia and Mark Kelly of Arizona, restocked their war chests with multimillion-dollar sums ($7.2 million and $6 million, respectively), according to new financial filings this week. That gives them an early financial head start in two key states where Republicans’ disagreements over former President Donald J. Trump’s refusal to accept his loss in 2020 are threatening to distract and fracture the party... Four Senate Democratic incumbents are up for re-election in swing states next year — making them prime targets for Republican gains. But in none of those four states — New Hampshire, Nevada, Arizona and Georgia — has a dominant Republican candidate emerged to consolidate support from the party’s divergent wings... The unexpected retirements of Republican senators in Pennsylvania and North Carolina have opened seats and opportunities for Democrats in those swing states, but the path to victory is complicated. In both, Democrats must navigate competitive primaries that pit candidates who represent disparate elements of the party’s racial and ideological coalition: Black and white; moderate and progressive; urban, suburban and more rural.