Global stock markets posted their biggest rally of the year Monday after a shift in sentiment raised hopes that Britain’s exit from the European Union may be avoided.

U.S. stocks swung higher following strong gains in Europe and Asia. The Dow Jones industrial average climbed 129.71 points, or 0.7 percent, to 17,804.87. The Standard & Poor’s 500 index rose 12.03 points, or 0.6 percent, to 2,083.25. The Nasdaq composite gained 36.88 points, or 0.8 percent, to 4,837.21. U.S. stocks were on pace for much larger gains earlier in the day. At one time the Dow was up 271 points.

European stocks soared, with the pan-European STOXX 600 closing up 3.7 percent and the FTSE 1000 index rising 3 percent. Asian stocks also climbed, with the benchmarch Japanese Nikkei ending up 2.3 percent.

New polls released over the weekend signaled that the campaign calling for Britain to stay in the EU had picked up momentum. A vote on the referendum is planned for Thursday.

Last week, when it seemed the “leave” campaign had the upper hand, market anxiety about a possible Brexit flared, marked by high trading volume and a surge of volatility.

The poll results over the weekend – showing that 45 percent of voters want to remain in the EU, compared with 42 percent in favor of a Brexit – gave markets a shot of optimism.

“What the market is telling you today is that, listen, they’re probably going to vote to stay, but it’s going to be close,” said John Canally, chief economic strategist for LPL Financial.

The latest change in sentiment followed a three-day hiatus in campaigning after a member of Parliament who supported staying in the EU was killed.

But as new polls emerge in the days before the vote, expectations could swing in either direction, said Dean Turner, an economist with UBS Wealth Management focusing on Britain.

Investors could also be swayed this week by comments from Federal Reserve Chair Janet Yellen, who is scheduled to testify before Congress on Tuesday and Wednesday, Canally said.