Republican lawmakers face a race against the clock to pass their controversial tax reform bill following the shock U.S. Senate seat win for Democrat Doug Jones in Wednesday's special election in Alabama.

The victory for Jones, a 63-year old lawyer who served as state Attorney General under former President Bill Clinton, could not only change the face of the Senate but also disrupt the broader agenda of President Donald Trump as he struggles to deliver his first major win legislative before the end of the year.

The U.S. dollar index, which benchmarks the greenback against a basket of six global currencies, traded modestly lower at 93.98 in overnight dealing, while Wall Street futures pulled back from record highs, as investors re-set expectations for the Senate's composition and, possibly, the fate of the President's tax cuts.

We don't underestimate what the #AlabamaElection outcome means for $USD political risks in a mid-term election year in 2018. It's a key pillar for our bearish US dollar view

— Viraj Patel (@VPatelFX) December 13, 2017

With at least two weeks for Alabama's Republican Governor, Kay Ivey, to certify the election win -- and perhaps longer if losing candidate Roy Moore challenges Jones' narrow victory -- GOP Senators will hold on to their 52-48 majority until at least Christmas, providing a narrow window within which they can finalized, pass and deliver a tax bill to the President's desk for a final signature.

Getting closer and closer on the Tax Cut Bill. Shaping up even better than projected. House and Senate working very hard and smart. End result will be not only important, but SPECIAL!

— Donald J. Trump (@realDonaldTrump) December 10, 2017

Furthermore, even if Ivey certifies the result immediately, Senate Majority Leader Mitch McConnell may not seat Jones in the chamber until next year, leaving lame-duck interim Senator Luther Strange in place for the final round of voting.

However, the bill has little public support at this stage and its fiscal implications -- including a $1.5 trillion addition to the federal deficit over the next 10 years -- have some Republican lawmakers sensing a shift in the national tone.

63% of U.S. residents, up from 57% in November, say they disapprove of how congressional Republicans are handling tax reform.

— Marist Poll (@maristpoll) December 12, 2017

Kentucky's Rand Paul, a high-ranking Republican, said Tuesday that he could not "in good conscience" support a bill that adds to the "to the already massive $20 trillion debt," suggesting he may not support the bill's final draft.

He later clarified his remarks to insist that tax cuts are "never the problem" as long as they included limits on federal spending, but his prevarication could be an omen for the President as he counts votes in the runup to Christmas.

Market reaction to Jones' election win may also be difficult to gauge in the near term, particularly given the fact that the Federal Reverse will hold its final policy meeting of the year later today in Washington - and the final press conference hosted by outgoing chair Janet Yellen - that is expected to include a more detailed forecast for 2018 rate hikes.

The U.S. Treasury is also in the midst of a massive $140 billion in debt sales this week which are altering price and yield movements in government bond markets all over the world, making it difficult to assess how of if they're reacting to what could be a game-changing win for the Democrats as the country heads to mid-term election next year.