It appears that Senator Brian Nieves (r) has drawn a primary. At 4:03 p.m. yesterday Representative Dave Schatz (r), who was first elected in the 61st Legislative District in 2010 (and not yet subject to term limits), filed as a candidate in the 26th Senate District, challenging Senator Nieves (r) in the primary.
Via the Missouri Secretary of State:

It interesting to note that ten minutes after Representative Schatz (r) filed for the Senate Justin Alfermann filed to replace Schatz as a republican candidate in the 61st Legislative District at 4:13 p.m.:

It’s all in the timing.
Representative Schatz (r) does not have a particularly low key legislative agenda (for the current session):
HB1093 Lant, Bill Schatz, Dave HB 1093 1/9/2014 Referred: Workforce Development and Workplace Safety
4567H.01I – Requires authorization for certain labor unions to use dues and fees to make political contributions and requires consent for withholding earnings from paychecks
HB1094 Lant, Bill Schatz, Dave HB 1094 1/9/2014 Referred: Workforce Development and Workplace Safety
4569H.01I – Specifies that no person as a condition or continuation of employment can be required to engage in or cease engaging in specified labor organization practices
HB1095 Lant, Bill Schatz, Dave HB 1095 1/9/2014 Referred: Workforce Development and Workplace Safety
4568H.01I – Specifies that no person as a condition or continuation of employment can be required to engage in or cease engaging in specified labor organization practices
HB1148 Hicks, Ron Schatz, Dave HB 1148 1/9/2014 Referred: Health Care Policy
4185H.01I – Requires an ultrasound to be conducted and reviewed with the pregnant woman prior to the 24-hour waiting period for an abortion
HB1478 Swan, Kathryn Schatz, Dave HB 1478 1/22/2014 Referred: Health Care Policy
5105H.02I – Changes the laws regarding the protection of women’s health care
HJR43 Lant, Bill Schatz, Dave HJR 43 1/9/2014 Referred: Workforce Development and Workplace Safety
4448H.01I – Proposes a constitutional amendment to prohibit public labor organizations from withholding sums from the earning of public employees for the payment of dues or fees without consent
HJR44 Lant, Bill Schatz, Dave HJR 44 1/9/2014 Referred: Workforce Development and Workplace Safety
4451H.01I – Proposes a constitutional amendment to prohibit employers from requiring persons to become members of a private labor organization as a condition of employment
HJR55 Hicks, Ron Schatz, Dave HJR 55 1/28/2014 Public Hearing Completed (H)
4677L.01I – Proposes a constitutional amendment protecting a citizen’s right to hunt, fish, and harvest wildlife and the use of traditional devices and methods to exercise the right
From 2013:
HB872 Schatz, Dave Kolkmeyer, Glen HB 872 4/23/2013 Public Hearing Completed (H)
2052L.01I – Removes the renewal requirements for concealed carry endorsements making them valid for life if not suspended or revoked
HB77 Burlison, Eric Schatz, Dave HCS HBs 77, 91 & 95 5/9/2013 Rules – Reported Do Pass (H)
0370H.05C – Specifies that no person as a condition or continuation of employment can be required to engage in or cease engaging in specified labor organization practices
HB350 Frederick, Keith Schatz, Dave HCS HB 350 4/24/2013 Rules – Reported Do Pass (H)
1071L.02C – Prohibits the publication of any identifying information of firearm owners and prohibits health care professionals from being required to inquire, document, or disclose a patient’s status as a firearm owner
HB378 Kelley, Mike Schatz, Dave HB 378 2/27/2013 Referred: Health Care Policy
1222L.01I – Prohibits a licensed pharmacy from being required to carry or maintain in inventory any specific prescription or nonprescription drug or device
HB386 McCaherty, John Schatz, Dave HB 386 3/13/2013 Voted Do Pass (H)
1187H.01I – Establishes the Abortion Ban for Sex Selection and Genetic Abnormalities Act of 2013 to prohibit an abortion solely due to the sex of the unborn child or a genetic abnormality diagnosis
HB400 Riddle, Jeanie Schatz, Dave HB 400 7/12/2013 Gov Took no Action, Sent to Sec of State/Article 3 Sec 31(H)
0839L.01T – Establishes requirements for the administration of RU-486 or any other abortion-inducing drug or chemical
From 2012:
HB1512 Curtman, Paul Schatz, Dave HB 1512 5/1/2012 Public Hearing Held (S)
5396L.01P – Establishes the Civil Liberties Defense Act which specifies how courts may rule in contractual disputes involving the laws of other countries and in jurisdictional issues involving other countries
HB1637 Curtman, Paul Schatz, Dave SCS HCS HB 1637 5/16/2012 Placed on Informal Calendar
5143S.06C – Establishes the Missouri Sound Money Act of 2012 which changes the laws regarding legal tender
HB1747 Wells, Don Schatz, Dave HB 1747 3/5/2012 Public Hearing Completed (H)
5867H.01I – Changes the laws regarding weapons
HB1933 McCaherty, John Schatz, Dave HB 1933 5/2/2012 Public Hearing Completed (H)
5798L.02I – Establishes the Abortion Ban for Sex Selection and Genetic Abnormalities Act of 2012 to prohibit an abortion solely due to the sex of the unborn child or a genetic abnormality diagnosis
HB2051 Cookson, Steve Schatz, Dave HB 2051 4/18/2012 Referred: Elementary and Secondary Education (H)
6277L.02I – Prohibits the discussion of sexual orientation in public school instruction, material, or extracurricular activity except in scientific instruction on human reproduction
HCR9 Curtman, Paul Schatz, Dave HCR 9 2/20/2012 Public Hearing Completed (H)
4379L.02I – Urges the United States Congress to pass the Federal Reserve Transparency Act to require a complete audit of the Federal Reserve
HJR49 Brattin, Rick Schatz, Dave HJR 49 4/30/2012 Public Hearing Held (S)
4422L.01P – Proposes a constitutional amendment specifying that the right of every citizen to possess or purchase ammunition and articles for the proper functioning of arms must not be infringed or limited
HJR64 Curtman, Paul Schatz, Dave HCS HJR 64 5/9/2012 Rules – Reported Do Pass (H)
4479L.02C – Proposes a constitutional amendment prohibiting any person, employer, or health care provider from being compelled to participate in any health care system
HJR72 Bahr, Kurt Schatz, Dave HJR 72 3/22/2012 Referred: General Laws (H)
5301L.01I – Proposes a constitutional amendment specifying that each citizen has an inherent liberty that includes being able to make decisions regarding lawful health care-related services or products
Gee, this stuff looks familiar.
As if there’s any substantive difference between the two?