Rob Portman of 2018

[JMT]

Out of the list provided, I would say Tammy Baldwin. Because Wisconsin voted for Trump and can be seen as a swing state, the GOP may enlist a top tier recruit to run against Baldwin. While the ideal candidate already said he isn't running (Sean Duffy), the GOP may very well turn to Eric Hovde. Hovde would be able to run as an "outsider businessman," he'd be able to self fund a campaign (which the party would appreciate, so they wouldn't have to place many funds towards this race) and he did fairly well in the GOP Senate primary 6 years ago and would be able to build on that support. There may be polls showing him running close to Baldwin, leading many to believe the race is competitive, but towards the end of the election cycle the anti-Trump mood will propel Democrats into office, including Baldwin. In this hypothetical (but very realistic) scenario, Baldwin would be the clear favorite by the time election day rolls around, making her the Rob Portman of 2018.