And make no mistake, there were few dollar lovers coming in to 2021. COVID vaccines had arrived to goose a global recovery and de-stress the financial system further, political risks around U.S. elections appeared to have passed and the Federal Reserve continued to "out print" other central banks in its bond buying and balance sheet expansion.
Global fund managers polled by Bank of America last month saw "short U.S. dollars" as the second most crowded trade on the planet, only behind U.S. tech stocks. And speculative hedge fund positioning recorded by the CFTC - negative since March - last week threw up its biggest net dollar short for almost four months.
But a combination of these position extremes and rising U.S. Treasury yields, fueled by ramped up fiscal stimulus bets as the Democrats swept up an unlikely Senate majority in Georgia last week, has prompted a rethink.
Morgan Stanley and Deutsche Bank teams at least switched long-standing negative dollar recommendations to neutral - even if Deutsche described the change as largely "tactical".
And yet investors clearly saw something shift right from the Senate results - at least partly because the new fiscal possibilities take pressure off the Fed.
"The prospect of more fiscal policy and less monetary stimulus should support the U.S. dollar," David Page, Head of Macro Research at AXA Investment Managers, said last week, adding that some of the 5% dollar drop since the November elections should now be unwound.
Lo and behold, the dollar index .DXY - which had virtually ignored steadily rising U.S. Treasury yields since August - burst 1.5% higher this week as nominal 10-year U.S. Treasury yields jumped almost 25 basis points to more than 1% for the first time since March.
Fed Vice Chair Richard Clarida virtually blessed the move on Friday by saying the Fed would not react to the breach of 1% - undermining any remaining speculation the Fed would implicitly adopt some rigid yield cap around those levels.
SPOILING THE NARRATIVE
But why the dollar suddenly reacted is less obvious as its role in the wider "reflation" narrative to date as been to weaken.
After all, if a Democrat sweep adds a fiscal spur alongside an inflation-tolerant Fed, then the presumption of accelerating consumer price rises down the line - enough to keep lifting stocks and commodities - should continue to sink the dollar too.
But it all pre-supposes inflation does indeed come through with gusto. And here the bond markets have been less clear cut than it seems at first glance.
While nominal Treasury yields have surged, market inflation expectations have moved less so because real, or inflation-protected, Treasury yields have moved higher too.
The implied 10-year inflation expectations embedded in that constellation topped 2% for the first time in two years. But they have stalled just above the Fed's target about 2.10%.
They remain well within levels seen over the past 10 years, when the Fed's favoured measure of core inflation never actually matched the breach on any sustainable basis.
The jury on inflation remains out. The pandemic is still raging, with swathes of spare capacity across economies to persist long after vaccines roll out. And we have yet to see details on U.S. fiscal firecrackers, let alone how a razor-thin Senate majority will hold.
As nominal rates stalked zero, sinking of U.S. 10-year real rates below -1.0% was a powerful driver of dollar weakness last year. If the Fed was to cap nominal yields, the argument went, then the only expression of inflation fears would be ever more negative real rates that would take the currency down with them.
But not only have real rates backed up above -1.0%, but the real rate U.S. premium over German and euro zone equivalents has risen to its highest this week since May 1.
And in the meantime, all the fiscal speculation has just brought forward the money market's assumed date for Fed policy rate re-tightening to earlier in 2023 than previously thought.
Neither development quite matches the "currency debasement" line so often cited as a reason to sell the greenback and load up on the likes of gold or even Bitcoin.
Of course many still assume the reflation narrative will prevail. And, even if not, a widening world recovery will undermine the dollar anyway - as UBS Global Wealth Management said on Tuesday.
Why does it matter The direction of the dollar - the "new VIX" as the Bank for International Settlements once called it - remains critical to global financial conditions in a world still heavily banked or borrowed in dollars and where energy, commodities and much trade are still denominated in greenbacks.
Rampant U.S. inflation and "dollar debasement" is clearly an historic game changer. But we're still a long way from here to there and even interest rate markets are hesitating.
(The author is editor-at-large for finance and markets at Reuters News. Any views expressed here are his own)
(by Mike Dolan, Twitter: @reutersMikeD. Including charts by Ritvik Carvalho and Saikat Chatterjee. Editing by Jane Merriman) ((firstname.lastname@example.org; +44 207 542 8488; Reuters Messaging: email@example.com))