Outgoing Delaware Governor Ruth Ann Minner did her successor Jack Markell a really big favor by appointing Joe Biden's replacement before she left office, because it's been tough times for the other Governors who have appointed Senators this year.
Rod Blagojevich is obviously the most well known example of this since he tried to sell the seat and then got impeached, but David Paterson in New York and Bill Ritter in Colorado have had more mundane issues with their political fortunes since making appointments to fill vacant seats.
When we polled Colorado in December, right after the news of Ken Salazar's cabinet appointment, Ritter had a 49% approval rating, including a 54% mark with Hispanic voters. But when we came back to the state in April, after the appointment, his approval had plummeted to 40%. Beyond that he was trailing Scott McInnis 48-41 in a hypothetical contest, including a 45-42 deficit among Hispanics, who may have been perturbed that Ritter didn't appoint another Latino to replace Salazar.
David Paterson's approval rating was above 50% in all but one New York poll conducted between the beginning of September and the middle of January. Then he by all accounts bungled the appointment of Hillary Clinton's replacement and since mid-February almost every approval poll has shown him with numbers in the 20s, with some even dipping into the teens. Paterson went from having held a solid lead in every poll testing him against Andrew Cuomo to getting clocked in all of them.
Blagojevich, Ritter, and Paterson's issues certainly aren't completely attributable to having to make Senate appointments but that played a big role. It's going to be very interesting now to see how Florida voters react to Crist's choice- you could argue that any fallout will be minimal because he is so popular- but Paterson had Crist like approval numbers before his appointment and that didn't stop them from plummeting. If Crist gets effectively attacked for cronyism by both the right wing of his party and Democrats, this could get interesting.