From the keyboard of showrunner Beau Willimon:

One of the big turning points for the show was when Claire derailed Russo's water bill, something that Frank never intended. This led to Frank being forced to de-rail Russo's bid for governorship and his final gambit of the season — to become the VP. We are led to believe that this was always his plan, to force a last minute implosion by Russo so that VP Matthews could be the only possible candidate in his home state and would step down from the VP role. But this plan doesn't match up at all with Frank's initial (seemingly genuine) efforts to win Russo the governorship, which was only derailed because of Claire's backstabbing. After all, if the water bill had been successful, it would have made it much more difficult for Frank to force Russo to withdraw his candidacy later in the campaign. So, what I want to know is, what was Frank's original plan with Russo before the Water Bill was lost? —KCHA237
Francis approaches politics like a jazz artist, not like a mathematician. He doesn’t always have every part of the equation mapped out. He seeks potential opportunities, not always sure where they’re headed. And he responds to the unexpected, transforming chaos into order. That said, he always had the intention of derailing Peter’s campaign. By doing that he could convince Matthews to run for governor, thereby opening the VP slot. But he hoped to derail it at the last minute — to give Walker the least amount of time to find a replacement. Matthews would have to step in. That’s why he wanted the Watershed Bill to pass — in order to keep Russo viable until it was time to pull the rug out from under him. What Claire did was accelerate the process, endangering Russo’s campaign earlier than Francis would have liked, and potentially leaving Walker too much time to replace Matthews once he got into the race. Francis had to adapt, to stall Walker. And he never planned on killing Russo. He hoped Russo would quietly go away. But Russo became unmanageable — a legitimate threat — so he seized an opportunity in the garage.

http://www.vulture.com/2013/04/your-...-answered.html