I started out my political life as a happy Democrat and staunch admirer of some great Democratic statesmen. I was an admirer of the honesty and integrity of Harry Truman whether or not I agreed with all his initiatives and decisions. I loved JFK's vision, fiscal conservatism, and statesmanship in the face of real international confrontation. But beginning with Lyndon Johnson and finally coming to a head with Carter, the Democratic Party absolutely left me when it began currying favor to buy votes by increasing the rewards for incompetence and nonproductivity while punishing competence and productivity. I was quite young, but I knew what I believed to be right, and I jumped on Reagan's band wagon--he was also a Democrat turned Republican--and I don't think either of us ever looked back.
So yes, you can trust people who jump parties out of conviction and not simply to increase their fortunes. But each time a conservative Democrat crosses over, it dilutes the GOP's more extreme right wing--that is not a bad thing--but it also makes it harder for the GOP leadership to stick with true reforms and practical conservatism to get us back on track.
And the Democratic Party becomes increasingly a party of left wingnuts farther and farther removed from what most American people believe and want.