By Paul Steinhauser
CNN Deputy Political Director
WASHINGTON (CNN) -- It's one of John McCain's closing arguments in his bid for the White House. The Republican presidential nominee suggests that Democrats will increase their majorities in Congress, and he warns of one-party rule by the Democrats if Barack Obama is elected president.
Fifty percent of likely voters say if Sen. Barack Obama wins the election, Democrats should control Congress.
1 of 2 McCain has said Obama is "working out the details" with Democratic leaders to raise taxes, increase spending and "concede defeat in Iraq."
But a new national poll suggests Americans may not be as concerned about one party if Obama wins the White House.
In a CNN/Opinion Research Corporation survey released Sunday, 50 percent of likely voters questioned said if Obama wins the White House, Congress should be controlled by Democrats, with 48 percent saying it should be controlled by Republicans.
But if McCain wins the presidential election, 59 percent said Congress should be controlled by Democrats, with 39 percent saying it should be controlled by Republicans.
The Democrats currently have a 235 to 199 majority in the House of Representatives and a 51 to 49 majority in the Senate -- the chamber's two independent senators are allied with the Democrats.
One of Obama's closing points is that McCain would carry out George Bush's policies if elected, saying, the Arizona senator has "ridden shotgun" with the president on economic policy.
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The poll suggests that 53 percent think McCain would mostly carry out Bush's policies, with 45 percent saying he would not. As for Bush, only 28 percent approve of the way he's handling his job as president.
Likely voters questioned in the poll were also asked whether Obama will win the election. Watch more on the final days of campaigning »
"Nine in 10 think it's likely; nearly half say it is very likely. Only 1 in 10 say it is very likely that McCain will win, while half say a McCain victory is unlikely," said CNN Polling Director Keating Holland.
How will Obama supporters react if he does not win on Tuesday? One in five will be angry; one in four will be upset but not angry. Most Obama supporters, however, say they will be disappointed but not angry or upset if McCain wins.
The poll also suggests the Democrats are much more excited about this election than Republicans. Forty-five percent of Democrats questioned said they are extremely enthusiastic about voting this year, compared to 28 percent of Republicans.
"The economy remains the No. 1 issue to most voters. But although 8 in 10 say that economic conditions are poor now, 62 percent say that the economy will be in good shape a year from now," Holland said.
"The economy, which is already a strong issue, jumped even further in importance after the financial crisis hit in September."
"And since the public tends to blame the Republicans more than the Democrats for that crisis, that event provided a boost not just to Barack Obama but to Democratic candidates across the country. Democratic congressional candidates have a 9-point lead in the 'generic ballot' question," added Holland.
The generic ballot asks voters their preference for U.S. House without naming the candidates running in each district.
The CNN/Opinion Research Corporation poll was conducted Thursday through Saturday, with 1,017 adult Americans questioned by telephone. The survey's sampling error ranges from plus or minus 3 percentage points to plus or minus 4.5 percentage points, depending on the question.