President Obama unveils his 2017 budget proposal today. It's an aspirational blueprint that details how he would set priorities if he controlled the government's checkbook ... which he doesn't.

"This budget is not about looking back at the road we have traveled," Obama said. "It is about looking forward."

But congressional Republicans are looking past the president. House Speaker Paul Ryan dismissed the budget as "a progressive manual for growing the federal government at the expense of hardworking Americans."

Here are five big things you need to know about Obama's eighth budget blueprint.

1. It's his last ... and least influential

The president's budget is invariably described as "dead on arrival" when it reaches Capitol Hill. This one got that label weeks earlier.

Republican leaders of the House and Senate Budget Committees don't even plan to hold a token hearing on the $4 trillion White House spending plan. Obama will be out of office less than four months into the budget year. And the roll-out of the budget itself is overshadowed by the New Hampshire primary.

2. More red ink

President Obama boasted in his State of the Union address of cutting the deficit as a share of the economy by three-quarters during his time in office. This year, however, the deficit is creeping up again — largely as a result of tax breaks extended by Congress at the end of 2015.

The president's budget projects that deficits will remain in a manageable range — less than 3 percent of GDP — for the next decade. That includes some rosy assumptions, though, about tax revenues, health care savings and immigration reform.

3. Domestic shots across the bow

The president's budget includes a variety of proposals designed to provoke a debate with Republicans. On the revenue side, these include a new $10/barrel tax on crude oil which would add up to 24 cents a gallon to the price of gasoline, higher taxes on capital gains, and a renewed push to close what the White House calls the "trust fund loophole." On the spending side, the president has proposed more investments in clean energy, mass transit, summertime meal subsidies for poor children, and expanded unemployment insurance.

4. Security spending, on the ground and online

Obama is seeking $11 billion for the battle against ISIS, $3.4 billion to shore up European defenses and discourage Russian aggression, and $19 billion to enhance the nation's cybersecurity.

5. A few nods to bipartisanship

While the overall budget is going nowhere, a few of its more modest ideas may have legs. The White House notes there's bipartisan support for accelerating cancer research, offering more treatment to people addicted to heroin and prescription pain medication, and expanding a tax credit to help low-income workers who don't have children.

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