If no presidential candidate wins a majority of electoral votes, who can choose the president.

http://www.usconstitution.net/const.html#A2Sec1

In addition to the above excellent answer please consider the following.

The lack of any candidate receiving a majority if the electoral college leads to what is called a contingent election. Scroll down to the section called "Election in the House and Senate". LWV | Who Will Elect the President?
The Electoral College SystemSection=Home&CONTENTID=2176&TEMPLATE=/CM/ContentDisplay.cfm

A problem soon emerged with what occurred in the election of 1800

Presidential Election of 1800 http://www.multied.com/elections/1800.html.

The above led to the 12th Amendment. This site gives you a copy of the 12th Amendment and also in the annotations explains the reasons for its issuance.

U.S. Constitution: Twelfth Amendment http://caselaw.lp.findlaw.com/data/constitution/amendment12/

a bill has been approved in the house and senate albeit in slightly different versions the bill now goes

If no presidential candidate wins a majority of electoral votes, the selection of the president falls to the House of Representatives. This is outlined in Article II, Section 1 of the United States Constitution. In a contingent election, each state delegation in the House is given one vote, and the candidate that receives the majority of the state votes (at least 26) wins the presidency. The Senate is responsible for selecting the vice president in this scenario.

To understand this process in more detail, you can visit the website http://www.usconstitution.net/const.html#A2Sec1. This site provides the full text of the United States Constitution, and you can navigate to Article II, Section 1 to read about the contingent election.

Additionally, you can visit http://www.multied.com/elections/1800.html to learn about the election of 1800 and the issues that arose as a result of no candidate receiving a majority of electoral votes. This historical event highlighted the need for changes in the electoral process, leading to the 12th Amendment.

The 12th Amendment to the United States Constitution outlines the procedure for electing the president and vice president in case of a tie or no majority. You can read the full text of the 12th Amendment and its annotations at http://caselaw.lp.findlaw.com/data/constitution/amendment12/, which provides both the text of the amendment and explanations for its issuance.

By exploring the resources provided, you will gain a comprehensive understanding of the contingent election process and the historical context behind it.