Acts of civility all around, really: Andrew Romanoff (former Democratic candidate for CO-SEN) decently invited Ken Buck (R CAND, CO-SEN) to his birthday party, and Ken graciously accepted that invite. The birthday party was also a debt retirement party - the Colorado (and national, of course) Democratic establishment of course has no intention of encouraging future challengers to their anointed picks - so Ken's present was along those lines. Nothing objectionable about that at all, if you're reasonable enough to recognize that there comes a time to put down the partisan rhetoric, particularly when the other side is holding out a legitimately conciliatory hand. Nothing objectionable, and perfectly reasonable.
Unless you're a hyper-partisan Lefty, of course. In that case, there's nothing left for you but to mutter dark comments about "party crashers" and mock the losers of your primary. And if you're the guy who has to depend on these hyper-partisan Lefties to win, you encourage them by starting a negative ad campaign against the guy who got an invite to a birthday party and had the effrontery to bring a present.
No wonder Bennett's now losing in the polls, apparently. Too much time around the Democrat establishment, I wager.