Will this hurt him in the 2014 election?
Given the allegations: yes.
Although there is little work on gubernatorial scandal as it relates to elections, the approval ratings of most politicians are hurt by scandal. For elections in the House of Representatives, Praino, Stockemer and Moscardelli found that members of Congress who had one or more of their actions referred to the House Ethics Committee were less likely to be reelected (49 percent) than those Members who did not have a case referred (87 percent). The specific type of scandal may matter also: corruption scandals led to an 8 percent reduction in vote share among Member of the House of Representatives while sex and financial scandals led to a 5 percent reduction in vote share.
Because of the alleged political collusion in this case and a very close election, this scandal may absolutely shrink enough support for Walker to lose the election.
Could he lose his governorship in the meantime?
Likely not, short of bombshell criminal charges filed forcing him to resign.
In a recent article, I charted the duration of gubernatorial scandals from 1972 to 2011 and examined the factors that ended an official’s career more quickly.
First, elected officials themselves (as opposed to appointees, nominees or staff) are more likely to survive a scandal. This is especially true for governors, which is good news for Walker.
Second, as opposed to other kinds of scandals (sexual, etc.), political scandals like Walker’s are harder to prove and don’t affect the survival of the governors involved in them.
Third, the more legislative opposition, the less the chance of surviving scandal. In this case, Wisconsin law requires two-thirds of the State Assembly to impeach and a majority of the state Senate to remove the governor from power. Since the Republican Party controls 60 percent of the State Assembly and 55 percent of the State Senate, Walker has a cushion.
Will this affect his presidential prospects?
Even if he survives in Wisconsin, keeps his position and wins reelection, the evidence suggests that his putative presidential campaign may take a hit, especially among his supporters.
In another article, using scandals connected to non-incumbent presidential aspirants from 1996 to 2012, I tracked the effect of each scandal on each campaign’s daily fundraising totals, competitive standing in the race and party endorsements.
Scandals involving Republican presidential candidates tended to be more damaging than for Democrats, especially in terms of fundraising and endorsements. For example, Republican candidates lose between one and two endorsements per day when a scandal is associated with the campaign.
The wide-open competition for the 2016 Republican presidential nomination is sure to produce many candidates, some viable and some not. A candidate hobbled by scandal may be late out of the starting gate and find him or herself lagging behind.
For more on political science research about scandals, see here.