President Donald Trump has decided to force an opening brawl with his opponents on an area of policy - immigration - that he sees as crucial to his re-election chances. But it's a risky, unpopular move that could end in retreat.
The Democratic leaders have refused to give in to Trump's demand for US$5 billion ($7.45b) towards his border wall. They are using the standoff to unify their congressional troops and show they won't be pushovers.
Before Christmas, funding for sections of the Government, including money for border security but no wall, looked locked in. The Senate passed the bipartisan proposal.
However, conservative commentators reminded Trump of the biggest promise of his 2016 election campaign. Trump vowed to build a wall on the southern border and said Mexico would pay for it. Fencing already covers about 1120km of the 3050km area. So far, no wall-building has occurred. Mexico has refused to pay for it.
Away from political rhetoric, figures from the Pew Research Centre show the number of unauthorised immigrants in the US has fallen from 12.2 million in 2007 to 10.7m in 2016. Border agents are apprehending fewer people.
For Trump it's all about keeping a key promise on an issue of importance to Republican primary voters. CBS polling in November found that 79 per cent of Republicans support it.
The wall is not a winning issue among the wider US electorate. In the Midterm campaign, Trump and Republicans hammered the migrant "threat" in the closing stages and lost 40 House seats.
The CBS poll found that 59 per cent of Americans overall oppose the wall. Independents oppose it by 66 per cent and Democrats 84 per cent.
As to how the US public feels about the shutdown, a Reuters poll found that 47 per cent blame Trump, 33 per cent blame Democrats in Congress and 7 per cent blame Republicans in Congress.
It also found that 35 per cent agreed with including money for the wall and 25 per cent agreed with Trump triggering the shutdown.
Trump is once again digging in, ignoring the many for the few, picking that his supporters will stick with him. If they do, an Electoral College victory in 2020 is a possibility.