Checks and balances encourage a spirit of bipartisanship and compromise between the president and Congress.

How does this work in practice?

Laws are passed, treaties are ratified, appointments are confirmed and budgets are fixed.

Examples

• George W Bush achieved his education reforms in 2001-02 because he worked with leading congressional Democrats such as Sen Edward Kennedy.
• Bill Clinton failed to get health care reforms through in 1993-4 because he adopted a partisan approach and ignored the views of even moderate Republicans.

However, gridlock can ensue.

Examples

• Many recent presidents have accused the Senate of rejecting or blocking their judicial nominations for partisan reasons.
• In 1995, parts of the federal government had to close when it ran out of money because of an impasse between Clinton and Congress.

Does this therefore lead to 'divided' government?

Yes:

Between 1969-2003 = 27 and a half years out of 34 of divided government. For only 6 and a half years of this period did one party control the president and both houses: 77-81 Carter and Jan-Jun 01 for GW Bush. This hasn't been the norm; before 1969, from 1935 onwards, there was divided government for only 8 years.

 Divided government (when president is different house to Congress) = less effective government e.g Bork, Clarence Thomas 1991 by Democrat-controlled Senate both supreme court nominees; impeachment proceedings against Clinton by Republican-controlled congress in 88-99 seem poor adverts for effective checks and balances.

Other problem is congress' power to declare war. Presidents have conducted wars in Korea, Vietnam and Persian gulf without Congress' declaration of war.

Impeachments were political.

Appointment of judges is too political.

No:

Not since 1935 has the Senate rejected a treaty of a president of its own party.

Only twice in past 50 years has congress overridden resolution of president of its party - 1964, when Johnson persuaded congress with democrat majorities in both houses to pass gulf of Tonkin resolution (during Vietnam war, Vietnam troops fired at an American ship and there were huge American casualties) to allow him to take whatever action he needed in south Vietnam. 

But checks and balances have stood the test of time, and are very difficult to change.