Glossary: US elections N-P
What is the difference between Medicare and Medicaid? What are blue dogs and red states? These are just a few of the many well-used but often misunderstood terms in US politics.
National convention The party assembly held every four years at which state delegates from across the country gather to nominate the party's candidates for president and vice-president.
The nominees are typically chosen by party voters in primary elections and caucuses well ahead of the conventions, but the formal convention processes remain in place in case the decision over the party's candidate has to be brokered by the various party leaders.
In 1924, a bitterly divided Democratic Party took 103 ballots to decide on their presidential candidate.
Oval Office The office traditionally occupied by the president in the West Wing of the White House.
The term is often used to describe the presidency itself, and the physical proximity of aides to the Oval Office is seen as reflecting the extent of their influence.
In addition to the Oval Office, the president keeps a private study next door.
Political Action Committee (Pac) An organisation formed to promote its members' views on selected issues, usually by raising money that is used to fund candidates who support the group's position.
Pacs monitor candidates' voting records and question them on their beliefs on issues of interest to their membership.
Because federal law restricts the amount of money an individual, corporation or union can give to candidates, Pacs have become an important way of funnelling large funds into the political process and influencing elections.
Pork barrel politics The appropriation of government spending - or pork - pursued by a lawmaker for projects that benefit his or her constituents or campaign contributors.
Primary A state-level election held to nominate a party's candidate for office. Regulations governing them and the dates on which they are held vary from state to state.
In some states, voters are restricted to choosing candidates only from the party for which they have registered support, however 29 states permit open primaries in which a voter may opt to back a candidate regardless of their nominal affiliation. In this case, strategic voting may take place with, for example, Republicans crossing over to back the perceived weaker Democratic candidate.
Primaries first emerged as a result of the so-called progressive movement of the early 20th Century, which argued that leaving the nomination process purely to party bosses was inherently undemocratic.
Pro-choice The term used for those who support a woman's right to choose abortion if she so wishes.
Most pro-choice politicians will usually seek to avoid the emotive issue of abortion itself, following instead the libertarian line that government has no place interfering in what should be a private decision.
The Democratic Party has been broadly supportive of the pro-choice movement. President Bill Clinton summed up his party's stance by saying abortions should be "safe, legal and rare".
Pro-life The term used to describe politicians and pressure groups opposed to abortion or allowing women to opt for abortion.
Some American advocates of the pro-life position believe abortion should only be allowed in cases where a pregnancy results from rape or incest. Others believe that abortion should be ruled out altogether.
The 1973 Roe v Wade decision by the US Supreme Court, which in effect legalised abortion in the US, is viewed by pro-life supporters as in contravention of the fundamental rights of the unborn child.
A more recent decision, 1992's Planned Parenthood v Casey, allowed states to limit access to abortion so long as they do not place an "undue burden".
Since then, conservative states have placed dramatic restrictions on abortion, for example by enacting waiting periods between an initial consultation with the provider and the actual procedure, or by requiring doctors to inform pregnant women about the appearance and characteristics of the foetus.
Public Funding Money supplied to campaigns from government coffers and administered by the Federal Election Commission.
This includes primary election matching funds, which match the money candidates have raised privately, and a grant for the general election, and grants to fund the major parties' conventions.
Presidential candidates who accept public funding must agree to spending limits. In the general election, candidates who accept public funds may not raise private money in addition to the grant, nor can they spend more than the grant (though some legal and accounting expenses and some of candidates' personal cash is exempt).
In 2008, Mr Obama became the first candidate to decline public funds for the general election because he calculated he could raise more on his own and did not want to be held to a $84.1m spending limit - including what he had already raised privately. Also, he feared attack from well-funded independent conservative groups not subject to spending limits.
To qualify for primary election matching funds, candidates need to raise at least $100,000 in individual donations, including at least $5,000 from 20 different states.
Candidates who fail to receive at least 10% of the popular vote in two successive primary elections lose their eligibility for continued payments, unless and until they receive at least 20% of the vote in a later primary.
The two major parties - the Democrats and Republicans - are automatically entitled to a public grant to pay for the cost of their national conventions. Minor parties are also entitled to a smaller subsidy in proportion to the vote they received. New parties are not eligible.
Purple state Another term for a swing state. A state which could vote Democratic (blue) or Republican (red).
Push polling The controversial practice where voters are contacted over the telephone by people who are ostensibly taking a poll, but who talk up their own candidate and rubbish opponents.