Start­ing Tues­day, the House is in ses­sion 13 days and the Sen­ate 14 be­fore the Au­gust re­cess be­gins. As con­gres­sion­al Re­pub­lic­ans face their long list of to-do items, one thing will weigh heav­ily on their minds: What will they tell their base if they don’t re­peal and re­place Obama­care, pass a sig­ni­fic­ant tax cut or tax re­form, ap­prove a ma­jor in­fra­struc­ture bill, or build a “Great Wall” between the U.S. and Mex­ico? What if none of these things hap­pen, and they still have a messy fight over rais­ing the debt ceil­ing, al­low­ing the Treas­ury De­part­ment to con­tin­ue to is­sue bonds, or passing a budget be­fore Sept. 30 to keep the gov­ern­ment run­ning?

The Re­pub­lic­an Con­gress can point to no sig­ni­fic­ant le­gis­lat­ive ac­com­plish­ments this year and very little pro­gress on its big prom­ises, un­less you count the House passing a health care bill that only 30 per­cent of Amer­ic­ans in last month’s Kais­er Fam­ily Found­a­tion Health Track­ing Poll viewed fa­vor­ably. (By com­par­is­on, the much ma­ligned and def­in­itely flawed Af­ford­able Care Act had a fa­vor­ab­il­ity rat­ing of 51 per­cent.) In oth­er words, if law­makers suc­ceed only in keep­ing the lights on, the wa­ter run­ning, and the toi­lets flush­ing, voters may won­der why they sent them to Wash­ing­ton in the first place.

On health care, Re­pub­lic­ans must choose between break­ing their prom­ise to re­peal and re­place Obama­care or en­act a sub­sti­tute that people hate even more. And while passing a big tax cut would be very pop­u­lar in many quar­ters, what if it came at the cost of driv­ing up an already sky-high de­fi­cit? And what about the ex­pect­a­tion that the GOP will straight­en out the un­wieldy tax sys­tem?

Re­pub­lic­ans are like the dog that caught the car. Now what? Pres­id­ent Trump and con­gres­sion­al Re­pub­lic­ans raised their sup­port­ers’ ex­pect­a­tions so high that fail­ing to de­liv­er could have pro­found con­sequences. In­ter­est­ingly, con­sumer-con­fid­ence polling shows that Re­pub­lic­ans are very op­tim­ist­ic about tax cuts and eco­nom­ic policies while Demo­crats are very pess­im­ist­ic about policy changes and worry about where the eco­nomy is headed. What if the Re­pub­lic­an faith­ful fig­ure out that very little is hap­pen­ing and not much is likely to hap­pen? Will Re­pub­lic­ans in gen­er­al and Trump sup­port­ers in par­tic­u­lar vote in the 2018 midterm elec­tions, or will they be no-shows like the Obama voters in 2010 and 2014?

The stakes for the 2018 midterm states are huge. Re­pub­lic­ans won­der how badly they’ll do in House, gubernat­ori­al, and state le­gis­lat­ive elec­tions and how well they can do in Sen­ate races. Demo­crats have 25 Sen­ate seats at risk, five in states that Trump car­ried by 19 points or more and five oth­ers that he car­ried by less­er mar­gins, while the GOP has only nine seats up next year and only one in a state that Hil­lary Clin­ton car­ried. So 2018 should be a his­tor­ic op­por­tun­ity for Re­pub­lic­an gains in the up­per cham­ber. A Re­pub­lic­an pres­id­ent with job-ap­prov­al rat­ings in the low- to mid-50s would likely mean GOP gains of at least three to five seats, maybe more. But with a pres­id­ent whose job-ap­prov­al rat­ings av­er­age around 39 or 40 per­cent and a GOP Con­gress that has little to show for it­self, 2018 could be an op­por­tun­ity lost for Sen­ate Re­pub­lic­ans.

Keep in mind that the House is up in its en­tirety every two years and thus is most re­spons­ive to the na­tion­al polit­ic­al cli­mate. Gubernat­ori­al and Sen­ate races of­ten turn on how many and which seats are in play, and what happened the last time and even the pre­vi­ous time that these seats were up. Be­cause gov­ernors serve four-year terms (ex­cept in Ver­mont and New Hamp­shire, where they’re in of­fice for two years), the seats up for grabs in 2018 were last filled in the midterms dur­ing Pres­id­ent Obama’s second term. These midterms were al­most as big a dis­aster as his first midterms. (In 2010, Re­pub­lic­ans swept to a House ma­jor­ity, and in 2014 they re­gained con­trol of the Sen­ate for the first time since 2006.) So Re­pub­lic­ans are hugely over­ex­posed to po­ten­tial losses in the gubernat­ori­al races be­cause of their suc­cesses in the last two midterms. In the Sen­ate, with its six-year terms, the shoe is on the oth­er foot. Demo­crats are hugely over­ex­posed be­cause of their enorm­ous gains in 2006—Pres­id­ent Bush’s hor­rif­ic midterms dur­ing his second term—and in 2012, when Obama won reelec­tion over Mitt Rom­ney by a wider mar­gin than an­ti­cip­ated.

The op­er­at­ive ques­tions are: How bad will it be for Re­pub­lic­ans in the House and gubernat­ori­al races, and how good will it be for the GOP in the Sen­ate? The short an­swer is that Re­pub­lic­ans bet­ter have a pretty im­press­ive list of mean­ing­ful-sound­ing ac­com­plish­ments to make up for what’s likely to be a largely empty plate on the big-tick­et items.

This story was originally published on nationaljournal.com on July 11, 2017

More from the Cook Political Report